1. Field of the Invention
The present invention relates to poultry vaccines and, more particularly, to a novel method of vaccinating poultry involving spraying with a live avirulent derivative of a enteropathogenic bacteria.
2. Description of Related Art
Contamination of poultry meat and eggs by enterobacterial human pathogens, such as Salmonella spp. is a well known cause of illness in humans when such contaminated products are consumed. The contamination occurs predominantly during processing of carcasses after slaughter by contact with intestinal contents that contain high levels of such enterobacteria. The enterobacteria colonize the intestinal tract, but do not normally cause disease in the poultry. In order to reduce the contamination of food with enteropathogens it would thus be desirable to diminish the amount of human enteropathogenic bacteria present in the intestinal tracts of market-age broilers. Efforts to reduce this contamination have focused on improved age broilers. Efforts to reduce this contamination have focused on improved sanitation during production and processing (Bailey, J. S., Poult. Sci., 72:1169-1173, 1993), but such techniques are time-consuming and expensive and are not totally effective in avoiding sporadic contamination. (See, e.g., Food Borne Disease Outlook Annual Summary, 1982; and Salmonella Surveillance Annual Survey 1992; both available from Center for Disease Control, U.S. Department of Health and Human Services, Atlanta, Ga.). Methods that depend upon sanitation during processing must be repeated frequently since processing equipment and personnel can be re-contaminated by each contaminated fowl that is processed. Methods that depend upon sanitation during production require constant vigilance due the high potential for contamination in the production environment. Therefore, a simple and inexpensive method to control enteropathogenic microbes in poultry during growth would be a key improvement in reducing carcass contamination during processing.
Promosopone et al., J. Food Protect., 61(2): 176-180, 1998, have reported that S. typhimurium colonization of the intestinal tracts of poultry can be reduced by administration of an avian-specific probiotic combined with S. typhimurium specific antibodies. Lactobacillus acidophilus, Streptococcus faecium and S. typhimurium-specific antibodies were administered by spraying the chicks at one day of age followed by oral administration via the drinking water from day 1 to day 3. The chicks were challenged by oral administration of S. typhimurium on day 1 and significantly reduced amounts of S. typhimurium were recovered from the cecum and colon following probiotic-treatment at 31, 38 and 43 days. Although administration of probiotic and antibodies as early as 1 day of age may have been important in reducing colonization of the intestine by S. typhimurium, it is not clear from this report whether the initial spray administration of probiotic and antibodies or the more commonly used oral administration in the drinking water on days 1-3 was responsible for decreasing S. typhimurium colonization.
Vaccines for use in preventing diseases in poultry have been reported and some of these vaccines are specific for Salmonella (See, e.g. U.S. Pat. Nos. 5,294,441, 5,389,368, 5,468,485 and 5,387,744). The methods for administration of vaccines in poultry vary, however, depending upon the target site of action of the active agent. In fact, it is commonly believed that the vaccination route should be tailored according to the preferential site of the microorganism for localization and replication. Thus, for Newcastle disease and infectious bronchitis viruses which multiply in the respiratory route, the vaccination methods of choice would be by eye drop into the eye, nasal passage and respiratory system of the chick or by the spray route. (Giambrone, World Poultry-Misset 13:19-23, 1997). Since many of the more important diseases of poultry occur in the respiratory tract, studies reporting on administration of spray vaccination for these diseases have used spray administration because an aerosol or spray is easily inhaled by the bird and thereby contacts the mucosal surfaces of the upper respiratory tract. Administration of vaccines for non-respiratory diseases, such as diseases of the tissues, circulatory system or gut, is usually by subcutaneous injection, or by oral administration, either by inoculation or by application in drinking water.
References disclosing the use of the spray administration of vaccines have almost exclusively been directed to immunizing against viral agents that invade through the respiratory tract such as, for example, to prevent Newcastle disease, avian encephalomyelitis, Marek""s disease, laryngotracheitis, infectious bronchitis and the like.
Bacterial vaccines, in particular live attenuated mutants derived from highly virulent bacterial parent strains, have also been used in poultry (Roland, K. et al., Efficacy of Salmonella typhimurium vaccine strains expressing Escherichia coli 078 lipopolysaccharide to protect against E. coli challenge in chickens, Abstract of a presentation at Conf. Of Res. Workers in Animal Diseases, Chicago, Ill., Nov. 10, 1997). Derivation of the attenuated mutant strain from a highly virulent parent increases the likelihood that the attenuated mutant will not only colonize the intestinal tract but also colonize the gut associated lymphoid tissue (GALT) and, elicit protective immunity. (See, e.g., Curtiss III et al., in Colonization Control of Human Bacterial Enteropathogens in Poultry, Blankenship et al., eds, Academic Press, Inc., New York, 1991 169-198). In contrast, bacteria that colonize the intestine but do not invade and colonize the GALT may not elicit an immune reaction. For example, studies in mice have revealed that lipopolysaccharide (LPS) O-antigen repeats on the surface of S. typhimurium are important not only to withstand nonspecific host defense mechanisms (Microbial Toxins, Vol. V, Roantree et al., eds., Academic Press, New York, 1971), but also for effective invasion through the mucin and glycocalyx covering the intestinal tract. As a consequence, rough mutants lacking LPS O antigens, when given orally, are unable to invade and colonize the GALT (See, e.g. Curtiss et al., 1991, supra).
Some references have reported on the administration of bacterial vaccines to poultry by oral or subcutaneous injection. For example, one commercial vaccine to prevent paratyphoid in pigeons comprises killed S. typhimurium administered by subcutaneous injection (Vetafarm Paratyphoid Vaccine, Vetafarm Pty. Ltd., Wagga Wagga, Australia). In addition, Curtiss et al, 1991, supra, report the use of an avirulent derivative of a pathogenic Salmonella as an orally administered vaccine in chicks.
Spray vaccination has also been reported for bacterial vaccines that cause respiratory diseases. Hertman et al. report on oral and aerosol administration of a Pasteurella multocida vaccine to chickens and turkeys to prevent fowl cholera, which is a respiratory tract disease (U.S. Pat. No. 4,169,886). Ley et al. report on eye-drop and aerosol administration of a vaccine containing live Mycoplasma gallisepticum, which produces a respiratory tract disease (Ley et al., Avian Diseases 41:187-194, 1997). A commercially available vaccine recommends administration of a vaccine containing an avirulent strain of E. coli serotype 078 to immunize against the respiratory disease caused by the wild-type parent (see Product Bulletin for GARAVAX(copyright)-T, Schering-Plough Animal Health Corp., Omaha, Nebr.). The use of an aerosol administration for all of these vaccines would have been selected because the underlying disease for which the poultry were being vaccinated involved infection of the respiratory tract.
Another reference reported that a vaccine containing a strain of the nonpathogenic E. coli K-12 lacking O-antigen could be administered as an aerosol (U.S. Pat. No. 4,404,186). Nevertheless, the K-12 strain is a laboratory-adapted strain and is not an enteropathogen and because this microbe has no ability to invade and colonize the gut associated lymphoid tissue, it is likely that any immunity elicited by this vaccine would have been due to immunization through the respiratory route.
Localized spraying of bacterial vaccines such as by nasal spraying or ocular spraying had been suggested in some references (for example, see U.S. Pat. No. 5,294,441). Nevertheless, none of this earlier work suggested the use of whole body spray administration of enteropathogenic bacterial vaccines.
Therefore, while spray-administered vaccines have been reported to be useful in controlling respiratory diseases in poultry, whole-body spray administration has not been suggested for vaccines in poultry for the control of human pathogens that are often present in and transmitted by poultry, but which are not the causative agents for respiratory disease in poultry.
Accordingly, it would be desirable to provide a method of reducing the contamination of poultry by enteropathogenic microbes, especially Salmonella spp., that would be easy and inexpensive to administer under normal commercial poultry production conditions; which could be administered to newly hatched chicks without individual handling; and which would reduce or prevent infection of visceral and lymphatic tissues and the intestinal tract of poultry by enteropathogenic microbes.
In accordance with the present invention, it has been discovered that vaccines can be administered to domestic birds by whole-body spraying of the birds with the vaccine. The vaccines are administered by this whole-body spray route in an amount that is effective in eliciting an immune response, i.e. antibody and/or cellular immunity. While virtually any vaccine can be delivered by this method, whole-body spray administration is surprisingly effective for vaccines comprising a live avirulent derivative of an enteropathogenic bacteria. Such enteropathogenic bacteria are preferably Salmonella species. This spray administration of enteropathogenic bacteria avoids some of the disadvantages of other routes of administrations in that it does not require individual handling of chicks, it can be administered on day-of-hatch, and is easy to use under conditions normally found in commercial poultry production.
The effective doses, which elicit an immune response, are unexpectedly low and roughly comparable to doses that are effective by the oral route of administration, such as administration in the drinking water. Typically, doses for administration of the live vaccines of the present invention are from about 105 to about 108 colony forming units.
The spray route of administration of the vaccines is applicable to vaccination of birds, such as chickens, at any age at which they are susceptible to the beneficial effects of the vaccine, but is especially applicable to birds that are of an age of 3 weeks or less, and, preferably, to birds of less than 1 day of age.
In some embodiments, the spray-administration can be followed by administration of the vaccine in at least one booster dose. Preferably such a booster dose can be administered orally by drinking water or by spray at about 14 days after administration by spray.
Preferably, the spray is a coarse spray of droplets having diameters in the range of from about 50 microns to about 150 microns.
In other embodiments the present invention is directed to a method for reducing microbial contamination of poultry. The method comprises immunizing the poultry against a microbial contaminant by whole-body spray administration of an immunogenic composition. The microbial contaminant may or may not be pathogenic to the poultry itself, however, when present in the poultry, such microbial contaminates can produce disease symptoms in humans consuming the meat or other food products produced from the poultry. The microbial contaminant can be any such contaminant, particularly, microbes that colonize the gastrointestinal tract of the poultry.
The immunogenic composition is administered in an amount that is effective in eliciting an immune response, i.e. antibody and/or cellular immunity against the microbial contaminant. Preferably, the immunogenic composition comprises a live avirulent derivative of an enteropathogenic bacteria. Such enteropathogenic bacteria are preferably Salmonella species.
The immunogenic composition is administered in doses, which are effective in eliciting an immune response. Such doses are roughly comparable to doses that are effective by the oral route of administration. Typically, doses for administration of the live vaccines of the present invention are from about 105 to about 108 colony forming units.
The spray route of administration of the immunogenic composition of the present invention is applicable to vaccination of birds of any age at which they are susceptible to the beneficial effects of the vaccine, but is particularly applicable to birds, such as chickens, at an age of 3 weeks or less, and, preferably, to birds of less than 1 day of age.
In some embodiments, the spray-administration can be followed by administration of the immunogenic composition in at least one booster dose by oral administration in the drinking water, preferably at about 14 days after administration by spray.
The spray is, preferably, a coarse spray of droplets having diameters in the range of from about 50 microns to about 150 microns.
Among the several advantages found to be achieved by the present invention, therefore, may be noted the provision of a new method for vaccinating a domestic bird using an enteropathogenic bacteria; the provision of a method for reducing the amount of colonization of the intestinal tract, lymphatic tissues and visceral tissues by enteropathogenic microbes, the provision of a method for reducing the microbial contamination of poultry destined for human consumption; the provision of a method that is easy and inexpensive to administer under normal commercial poultry production conditions; and the provision of a method that that allows administration to young, especially day-of-hatch chicks without individual handling.